1. Technical Field
The present invention relates to a composition for forming an alignment film used during formation of an alignment film by a droplet discharge method, and to a method for manufacturing a liquid crystal device using the composition for forming an alignment film.
2. Related Art
A liquid crystal device for holding a liquid crystal between a pair of substrates is provided with an alignment film for orienting the liquid crystal molecules in a prescribed direction in the surface of the substrate. Flexography and spin coating are commonly used as methods for forming a conventional alignment film. In flexography, damaged flexographic plates for printing and foreign matter deposits are factors that cause printing defects, and it is therefore laborious to handle and maintain the plates. There is a problem in that a considerable amount of printing material is required in order to spread the printing material on a flexographic plate, and the method is wasteful. There is a problem in spin coating as well in that the material that actually contributes to film formation is about 10% of the applied material, most of the applied material initially ends up being discarded, and wasted material is therefore considerable.
Droplet discharge methods are being closely examined in order to reduce such wasted applied material, the methods being typified by the inkjet method that can distribute a required amount of ink in required locations.
In order to form an alignment film using the droplet discharge method, a composition for forming an alignment film is dissolved in a suitable solvent to form a solution, the solution is discharged onto a substrate using the droplet discharge method, and the deposited solution is heated and dried to remove the solvent component, whereby a film is formed and an alignment film is obtained. The resulting alignment film is rubbed or subjected to another orientation treatment in order to orient the liquid crystal molecules in a prescribed direction as required.
Japanese Laid-Open Patent Application No. 2003-295195 discloses compositions for forming an alignment film suitable for the droplet discharge method can be dissolved in a solvent which contains at least one compound selected from γ-butyrolactone and butyl cellosolve and in which the ratio of the total content of the solvent accounts for 90 wt % or more of the entire solvent.
Japanese Laid-Open Patent Application No. 2006-30961 discloses a vertical liquid crystal alignment agent having a first organic solvent that contains a nitrogen atom in the molecule, the tensile strength being 39 dyne/cm or higher; a second organic solvent that does not contain a nitrogen atom in the molecule, the tensile strength being 39 dyne/cm or higher; and a third organic solvent in which the surface tension is 32 dyne/cm, as well as polyimide and/or a partially-imidized polyamic acid polymer.